I have looked through the support and have found this line of CSS to centre the #main-navigation menu

.sf-menu ul {
display: table;
margin: 0 auto;
}

This works for the desktop site however when accessed via mobile/IOS it leaves the menu open, i have left this CSS in for troubleshooting. Is there any way to have this centred on desktop and keep the menu closed (until clicked on) on mobile site?